Spin tool in Blender 2.92.0 rotates only around z-axis by default
Click outside to use view axis.

Spinning around camera view, undo, then TOP ortho.
There may be some magic to using the gizmo that appears if you click a plus, revealing the default Z axis path, but it is a slippery beast and TBH I have no idea how to control it. (apart from moving the pivot point)  Perhaps someone will add a better answer re this..
So I resort to align the view to axis I wish to spin around, then click outside the gizmo and spin around similarly to rotation.